California seeks to improve safety of 1,3-dichloropropene fumigant

California plans to restrict use of the fumigant 1,3-dichloropropene (1,3-D) because of human health concerns, including risks of cancer for people downwind of agricultural fields where it is sprayed. The measures would also reduce air emissions of 1,3-D, a volatile organic compound that contributes to the formation of ground-level ozone and poor air quality.

The restrictions include mandatory distances from occupied structures where the pesticide cannot be applied, soil moisture requirements, and a ban on nonagricultural uses.

Environmental and farmworker groups say the measures, proposed in November by California’s Department of Pesticide Regulation, don’t go far enough. At a hearing Jan. 18, farmworkers and health advocates urged California to ban all uses of 1,3-D. Farmers raised concerns at the hearing that requirements related to soil moisture would waste water resources that are in short supply and make the fumigant less effective.

1,3-D is widely used in California to kill nematodes and other pests in soil before strawberries and other crops are planted. The pesticide is prohibited in many countries, including those in the European Union. Its use in the US increased in 2005, after the fumigant methyl bromide was phased out because of concerns about its ability to deplete the Earth’s ozone layer.

California’s proposed restrictions go beyond those required by the US Environmental Protection Agency. In 2020, the EPA downgraded its classification of 1,3-D from “likely to be carcinogenic to humans” to “suggestive evidence of carcinogenic potential.” In August, the agency proposed allowing 1,3-D to stay on the market with the less protective cancer classification.